High accuracy temperature sensor
A temperature sensor is disclosed. In one aspect, the temperature sensor provides a digital output having a precise degree/code step. For example, each step in the digital output code may correspond to one degree Celsius. In one aspect, a temperature sensor comprises a precision band-gap circuit and a sigma delta modulator (SDM) analog-to-digital convertor (ADC). A bandgap voltage and a PTAT voltage may be provided from the band-gap circuit as an input to the SDM ADC. The SDM ADC may produce an output based on the difference between the PTAT voltage and the bandgap voltage. The temperature sensor may also have logic that outputs a temperature code based on the output of the SDM ADC.
Latest SanDisk Technologies LLC Patents:
- READ SCHEMES WITH ADJUSTMENT FOR NEIGHBORING WORD LINE SANITIZATION
- NON-VOLATILE MEMORY WITH DUMMY WORD LINE ASSISTED PRE-CHARGE
- WAFER HOTSPOT-FIXING LAYOUT HINTS BY MACHINE LEARNING
- Ferroelectric devices including a single crystalline ferroelectric layer and method of making the same
- Non-volatile memory with narrow and shallow erase
This present application claims priority from Indian Patent Application No. 201641007655, entitled, “HIGH ACCURACY TEMPERATURE SENSOR,” filed Mar. 4, 2016, incorporated by reference herein in its entirety.
BACKGROUNDSemiconductor devices are expected to operate over a wide temperature range. However, various electrical components exhibit a temperature dependence. For example, temperature affects many transistor parameters, the dominant among which is the threshold voltage.
As one example, in NAND flash memory devices, temperature variations present various issues in reading and writing data. A memory device is subject to varying temperatures based on the environment in which it is located. For example, some memory devices are rated for use between −40° C. and +85° C. Devices in industrial, military and even consumer applications may experience significant temperature variations. Temperature variations can cause read errors and widen the threshold voltage distributions of the different states of a non-volatile storage element.
Many other types of semiconductor devices have a need for temperature sensors.
Like-numbered elements refer to common components in the different figures.
A temperature sensor is disclosed herein. Temperature sensors, in general, require trimming to achieve high accuracy. This trimming may be performed at one or more reference temperatures. Trimming may be performed at two temperatures to increase the accuracy. However, trimming at two temperatures may increase cost. A part of the additional cost may be for specialized and expensive test setup external to the device under test. In one embodiment, trimming of a temperature sensor uses a single temperature trimming.
A temperature sensor may provide a digital output from which temperature can be calculated using an equation. In one embodiment, a temperature sensor provides a digital output having a precise amount of degrees/code step. For example, each step in the digital output code may correspond to one degree Celsius, 0.5 degrees Celsius, 2 degrees Celsius or some other fixed amount of degree Celsius per digital code. This allows the temperature to be more easily calculated from the digital output. This can save on hardware used to calculate the temperature from the digital output of the temperature sensor.
In one embodiment, a temperature sensor comprises a precision band-gap circuit and a sigma delta modulator (SDM) analog-to-digital convertor (ADC). The precision band-gap circuit produces a bandgap voltage that is one input of the SDM ADC. The temperature sensor may also comprise a proportional to absolute temperature (PTAT) circuit. The PTAT circuit produces a PTAT voltage that is also provided as an input to the SDM ADC. Note that the precision band-gap circuit and the PTAT circuit may share common circuitry. The SDM ADC produces an output based on the difference between the PTAT voltage and the bandgap voltage, in one embodiment. The temperature sensor may also have logic that outputs a temperature code based on the output of the SDM ADC.
In one embodiment, using the difference between the PTAT voltage and the bandgap voltage as an input to the SDM ADC helps to establish a desired temperature for the lowest temperature code. The following example will be used to illustrate. It might be expected that a device might be operated between about −40 degrees Celsius to about 125 degrees Celsius. This range is about 165 degrees. If each bit in the temperature code is to correspond to 1 degree Celsius, the temperature code should be at least eight bits. Moreover, for some devices, the middle code (e.g., 1000_0000 using an eight bit temperature code as an example) might be assigned a specified temperature (e.g., 85 degrees Celsius). This means that the lowest code (0000_0000 in the present example) should correspond to −43 degrees Celsius. Having the SDM ADC produce an output based on the difference between the PTAT voltage and the bandgap voltage helps to establish a target temperature (e.g., −43 degrees Celsius) for the lowest code.
In one embodiment, in which a PTAT voltage and a bandgap voltage are inputs to a SDM ADC in a temperature sensor, the bandgap voltage is scaled. Scaling the bandgap voltage helps to establish a relationship of one degree Celsius per bit in the temperature code, in one embodiment. The relationship could be some other fixed amount of degrees Celsius per bit in the temperature code. The bandgap voltage is scaled by the size of certain capacitors in the SDM ADC, in one embodiment.
In one embodiment, single temperature trimming of a temperature sensor having an SDM ADC is performed. The SDM ADC may input a bandgap voltage, which may be compared to a PTAT voltage. The SDM ADC may have capacitors (e.g., scaling capacitors) that are used to scale the bandgap voltage. The single temperature trimming may include trimming the band gap voltage, trimming the scaling capacitors, and trimming the PTAT voltage. In one embodiment, the trimming order is to first trim the band gap voltage, then trim the scaling capacitors, and then trim the PTAT voltage.
Some applications require a fast measurement of a physical parameter (e.g., temperature, voltage, pressure), but can tolerate a lower resolution measurement. Other applications require a higher resolution measurement, but can tolerate a slower measurement. One embodiment includes a sensor that can provide multiple resolutions, based on the output of the same analog-to-digital converter. The sensor may comprise a sigma delta modulator (SDM) ADC that outputs a digital reading. When the digital reading is first output by the SDM ADC, it may not be very accurate. The SDM ADC may update the digital reading (e.g., each clock cycle), such that the digital reading becomes more accurate over time. The output of the SDM ADC may comprise a bus having a width that is equal to the desired highest resolution of the digital code for the physical parameter. The sensor may further comprise a storage unit for each desired level of resolution. The sensor may further comprise logic that causes the storage units to sample the output bus after a certain number of clock cycles in order to store a digital code having a number of bits equal to the resolution. Thus, a faster, lower resolution reading may be obtained or, alternatively, a slower, higher resolution reading may be obtained.
The reference generator 204 generates a voltage that is proportional to absolute temperature (VPTAT), as well as a reference voltage (VREF). In one embodiment, VREF is a bandgap voltage (e.g., VBG). VPTAT may be based on the bandgap voltage. In one embodiment, reference generator 204 is offset compensated. Offset compensation may compensate for non-ideal factors in the components that make up reference generator 204. For example, there may be mismatches between transistors, diodes, resistors, etc., for which compensation may be provided.
The reference voltage may be a constant voltage regardless of factors including, but not limited to, power supply variations, temperature changes, and circuit loading, in one embodiment. Thus, VREF is temperature independent, in one embodiment.
As noted, in one embodiment, VREF is a band gap voltage (VBG). In one embodiment, the reference generator 204 comprises a band gap voltage circuit. As one example, a band gap voltage circuit may output a voltage close to the bandgap of silicon at 0 degrees Kelvin. Thus, VREF could be about 1.25 volts, using the bandgap of silicon as an example. However, note that VREF is not limited to being a band gap voltage.
The SDM ADC 206 inputs VPTAT and VREF and outputs a “n bit” temperature code (Temp<n−1,0>). In one embodiment, the SDM ADC 206 uses sigma delta modulation. In one embodiment, SDM ADC 206 is a single bit SDM ADC. In one embodiment, SDM ADC 206 is a first order SDM ADC. In one embodiment, SDM ADC 206 is a first-order, single-bit SDM ADC. In one embodiment, VPTAT is input to one input (e.g., non-inverting input) of a differential amplifier in the SDM ADC 206 and VREF is input to another input (e.g., inverting input) of the differential amplifier in the SDM ADC 206. This may be stated as using VPTAT−VREF as an input (e.g., temperature input) of the differential amplifier. As noted, VREF is a bandgap voltage, in one embodiment. VPTAT is an analog signal, in one embodiment. VREF may be referred to as a “reference signal.”
In one embodiment, the SDM ADC 206 uses sigma delta modulation to generate an output based on a difference between VPTAT and VREF. As noted, VREF may be a bandgap voltage. Hence, SDM ADC 206 may generate an output based on a difference between VPTAT and a bandgap voltage.
The control logic 208 controls the operation of the reference generator 204 and the SDM ADC 206, in one embodiment. The control logic 208 inputs a clock signal (“Clock”), as well as various control signals (“Control”). In one embodiment, SDM ADC 206 updates Temp<n−1,0> once each clock cycle. However, a different update rate can be used. In one embodiment, Temp<n−1,0> becomes more accurate with a greater number of clock cycles.
The band gap circuit 204a comprises diodes D1, D2 and D3. There is a 1:N ratio been diode D1 and diode D2. There is a 1:M ratio been diode D1 and diode D3. The cathodes of the three diodes D1, D2 and D3 are connected together. One side of variable resistor 220 is connected to the cathodes of diodes D1, D2 and D3. The diode cathodes are connected to ground, in one embodiment. The voltage at the other side of variable resistor 220 is VPTAT. The anode of diode D3 is connected to one side of a variable resistor 222. The voltage at the other side of variable resistor 222 is a bandgap voltage VBG. The anode of diode D2 is connected to one side of resistor 224.
The band gap circuit 204a also comprises transistors 210, 212, 213, and 214. In one embodiment, transistors 210, 212, 213, and 214 are MOSFETs. In this example, transistors 210, 212, 213, and 214 are PMOS transistors. The sources of transistors 210, 212, 213, and 214 are connected to a node that provides a supply voltage. The drains of transistors 210, 212, 213, and 214 are connected to DEM switches 218. It is possible for there to be some mismatch between transistors 210, 212, 213, and 214 due to, for example, process variation. The DEM switches 218 may be used to cancel such differences, as will be discussed below.
The band gap circuit 204a also comprises transistors 228 and 230. In one embodiment, transistors 228 and 230 are MOSFETs. In this example, transistors 228 and 230 are NMOS transistors. The sources of transistors 228 and 230 are connected to switches 226. It is possible for there to be some mismatch between transistors 228 and 230 due to, for example, process variation. The switches 226 may be used to cancel such differences. In one embodiment, switches 226 are used to alternate which transistor (between 228 and 230) is connected to diode D1 and which is connected to resistor 224. At one point in time, the source of transistor 228 may be connected to the anode of diode D1 and the source of transistor 230 may be connected to resistor 224. At another point in time, the source of transistor 228 may be connected to resistor 224 and the source of transistor 230 may be connected to the anode of diode D1. The switches 226 may be controlled by signals ϕa and ϕb.
Switch 232 may be used to connect the drain of transistor 230 to the gates of transistors 228 and 230. This switch 232 is controlled by signal ϕb. Switch 234 may be used to connect the drain of transistor 230 to the gates of transistors 210, 212, 213, and 214. This switch 234 is controlled by signal ϕa. Switch 238 may be used to connect the drain of transistor 228 to the gates of transistors 228 and 230. This switch 238 is controlled by signal ϕa. Switch 236 may be used to connect the drain of transistor 228 to the gates of transistors 210, 212, 213, and 214. This switch 238 is controlled by signal ϕb.
As noted above, the DEM switches 218 may be used to provide offset cancellation for transistors 210, 212, 213, and 214. The DEM switches 218 may rotate which of the transistors 210, 212, 213, and 214 is connected to the following nodes: the drain of transistor 228, the drain of transistor 230, resistor 220, and resistor 222. At any one point in time, the source of each transistor 210, 212, 213, and 214 may be connected to one of these four nodes. The DEM switches 218 are controlled by signals ϕDEM<3:0>.
The SDM ADC 206 includes a differential amplifier 240, six capacitors C1, C2, C3, C4, C5, and C6. Also included is comparison logic 248 and numerous switches 251-260. In one embodiment, capacitors C1 and C2 have the same capacitance. In one embodiment, capacitors C3 and C4 have the same capacitance. Note that capacitors C3 and C4 have a variable capacitance, in this embodiment. That is, the capacitance of capacitors C3 and C4 may be configured to a desired value. In one embodiment, capacitors C5 and C6 have the same capacitance.
In one embodiment, the magnitude of VBG is scaled by capacitors C1-C4. C1-C4 are one embodiment of a switched capacitor network. Scaling VBG may help to achieve a one degree Celsius step between each digital code that is output by the sensor 142, in one embodiment. The scaling may be used to achieve some other fixed amount of degrees Celsius between each digital code. In one embodiment, the magnitude of VBG is scaled by a “scaling factor” referred to as “K”. As one example, to obtain a code of 1000_0000 at 85 degrees Celsius, the following expression may hold (for 85 degrees Celsius): K*VBG=2(VPTAT−VBG). A more general expression for the scaling factor K, in one embodiment, is: K*VBG=(VPTAT−VBG)*RES*(2^N)/(TTARG−TMIN). In this equation, TMIN is the minimum temperature of measurement, TTARG is the target or trimming temperature, RES is a resolution in degrees Celsius per code, and N is the number of bits in the output temperature code. For example, if TMIN=−43 degrees Celsius and TTARG is 21 degrees Celsius, then for a one degree Celsius resolution per code and an eight bit output code: K*VBG=(VPTAT−VBG)*1*(256)/(25−(−43))=4 (VPTAT−VBG). Thus, it may be stated that the scaling factor K depends on (VPTAT−VBG)/VBG. Note that VBG may also be referred to as a reference voltage. The dependency of the scaling factor K may be based on factors including, but not limited to, TMIN, TTARG, RES, and N. In one embodiment, the scaling factor is realized by the capacitor ratio: C3,4/C1,2=K. In this example, C3,4 refers to the capacitance of capacitors C3 and C4, which are the same in one embodiment. In this example, C1,2 refers to the capacitance of capacitors C1 and C2, which are the same in one embodiment.
Differential amplifier 240 is a fully differential amplifier in the embodiment of
Capacitor C5 is connected between the non-inverting input and output 264 of the fully differential amplifier 240. Capacitor C6 is connected between the inverting input and output 262 of the fully differential amplifier 240. Capacitors C5 and C6 have the same capacitance, in one embodiment. Capacitors C5 and C6 have about the same capacitance as capacitors C1 and C2, in one embodiment. However, it is not required that C5 and C6 have about the same capacitance as capacitors C1 and C2. Capacitors C5 and C6 may be referred to as integrating capacitors.
Switch 260 is used to connect the non-inverting input of amplifier 240 to Node B. Switch 257 is used to connect the inverting input of amplifier 240 to Node A. Capacitors C1 and C3 each have one side connected to Node B. Capacitors C2 and C4 each have one side connected to Node A.
A common mode voltage (VCM) is provided to several locations in the SDM ADC 206. Several of the switches connect various points in the SDM ADC 206 to a node that provides the common mode voltage. Switch 259 connects Node B to VCM. Switch 258 connects Node A to VCM. The side of the capacitor C3 that is not connected to Node B is switchably connectable to VCM using switch 251. The side of the capacitor C4 that is not connected to Node A is switchably connectable to VCM using switch 256. The side of the capacitor C1 that is not connected to Node B is switchably connectable to VCM using switch 265. The side of the capacitor C2 that is not connected to Node A is switchably connectable to VCM using switch 266.
The sides of the capacitors C1-C4 that are not connected to either Node A or B are also switchably connectable to switches 270. Switch 252 connects capacitor C3 to switches 270. Switch 253 connects capacitor C1 to switches 270. Switch 254 connects capacitor C2 to switches 270. Switch 255 connects capacitor C4 to switches 270.
Control logic 208 outputs one or more temperature codes. In one embodiment, control logic 208 has a counter that counts the ones in the COMPOUT signal in order to determine the temperature code. As one example, if the COMPOUT signal has an equal number of ones and zeros, this may corresponds to a middle code. A middle code refers to one half way between the lowest and highest digital code.
In this example, control logic 208 outputs temperature code TEMP<7:0>. Control logic 208 outputs ready signal READY to indicate that temperature code TEMP<7:0> is ready, in this embodiment. Temperature code TEMP<7:0> may be an eight bit temperature code. In one embodiment, there is a one degree Celsius step size between each value in the eight bit temperature code. However, there could be some other relationship, such as two degrees Celsius step size between each value in the eight bit temperature code, 0.5 degrees Celsius step size between each value in the eight bit temperature code, or some other amount of degrees Celsius step size between each value in the eight bit temperature code. It is not required that there be a fixed amount of degrees Celsius step size between each value in the eight bit temperature code.
Switches 270, switches 251-260, DEM switches 218, and switches 270 may be implemented in a variety of ways, including, but not limited to transistors. Control logic 208 may be implemented in any combination of hardware and/or software. Control logic 208 may include various elements including, but not limited to, a state machine, a processor, digital logic, analog components, an ASIC (Application Specific Integrated Circuit), RAM, and/or ROM. In one embodiment, the RAM, and/or ROM may contain instructions that may be executed on the processor. The instructions could be stored external to the control logic 208. However, it is not required for control logic 208 to be implemented by software. In one embodiment, control logic 208 is implemented entirely by hardware. In one embodiment, control logic 208 is implemented at least in part by state machine 112 (see
In one embodiment, trimming of the sensor 142 is performed. In one embodiment, the trimming includes trimming the bandgap voltage (BG), trimming capacitors C3, C4, and trimming VPTAT. The trimming takes place in that order, in one embodiment. In the example depicted in
Bandgap circuit 204b comprises transistors 271, 272, 275, 276. In one embodiment, transistors 271, 272, 275, 276 are MOSFETs. In this example, transistors 271, 272, 275, 276 are PMOS transistors. The sources of transistors 271, 272, 275, 276 are connected to a node that provides a supply voltage (VSUPPLY). The drains of transistors 271-272 are connected to switches 277. The drains of transistors 275-276 are connected to switches 278.
Switches 278 are configured to rotate the connections of the drains of transistors 275 and 276 between resistors 220 and 222. Switches 278 are controlled by the signal “CHOP.” In one embodiment, the signal “CHOP” is implemented with the signals ϕa and ϕb in
Switches 277 are configured to rotate the connections of the drains of transistors 271-272 between the anode of diode D1 and resistor 224. At any one point in time, the drain of one of transistors 271-272 is connected to the anode of diode D1 and the drain of the other of transistors 271-272 is connected to the node of resistor 224 that is not connected to diode D2. Switches 277 may be controlled by the signal “CHOP.” In one embodiment, the timing for the signal “CHOP” is implemented with the signals ϕa and ϕb in
The bandgap circuit 204b also has an amplifier 279 with switches 281 at its input. The output of amplifier 279 is connected to the gates of transistors 271-276. In one embodiment, amplifier 279 has an inverting input and a non-inverting input (not depicted in
The signal ϕDEM<3:0> controls operation of switches 291-294. At any one point in time, each input is connected to one output. The signal ϕDEM<3:0> rotates which connecting line 296-299 each of the switches 291-294 is connected to. Thus, the inputs (IN1 IN4) are rotated between the various outputs (OUT1-OUT4).
In one embodiment, IN1 is connected to the drain of transistor 210 (see
As can be seen, at most one of the ϕDEM signals is high at one time. There is a gap between ϕDEM<0> and ϕDEM<1>. In this example, the time gap is 2 microseconds, but this is implementation dependent. In this example, ϕDEM<0> is high for about 32 clock cycles. The other ϕDEM signals (1, 2, 3) are also high for about 32 clock cycles.
Only one of signals ϕa, (kb are high at one time. The signal ϕa is high for about 128 clock cycles. Note that this corresponds to the time for each of ϕDEM<0> to ϕDEM<3> to go high once. There is a gap between ϕa goes low and (kb goes high. The signal (kb is high for about 128 clock cycles. Note that this corresponds to the time for each of ϕDEM<0> to ϕDEM<3> to go high once.
In one embodiment, a fast measurement of the temperature code is produced based on the output of the SDM-ADC after 32 clock cycles. This may be a lower resolution temperature code, such as a 5 bit digital code. In one embodiment, a higher resolution measurement of the temperature code (relative to the fast measurement) is produced based on the output of the SDM-ADC after 128 clock cycles. This higher resolution temperature code, could be an 8 bit digital code. This is further expanded upon below.
In one embodiment, the signals in
Note that the bandgap circuit 204a (
The comparator 248 receives a signal “COMP”, which instructs comparator 248 when to perform a comparison of the voltage at node 264 with the voltage at node 262. The comparator 248 outputs a signal on OUT and OUTN. OUT and OUTN are compliments, in one embodiment. For example, when OUT=1, OUTN=0, in one embodiment. In one embodiment, the number of “1s” at the OUT are counted to determine the temperature code.
In step 704, the bandgap voltage is trimmed. In one embodiment, resistor 222 of either
In step 802, a trim voltage (VTRIM) and the bandgap voltage are provided to the SDM ADC 206. In one embodiment, VTRIM has a magnitude that is based on the target value for the bandgap voltage. In one embodiment, VTRIM−VBG(target)=½ VBG(target). For example, VTRIM might be 1.8V and VBG(target) might be 1.2V. In this case, the goal of process 800 may be to adjust VBG (in the bandgap circuit 204a, 204b) until the temperature code that is output by the temperature sensor reaches a “half code” that is midway between the lowest and highest temperature code.
The comparator 248 may then produces an output (e.g., COMPOUT) based on the input to the SDM ADC 206 (as processed by SDM ADC 206). Stated another way, the comparator 248 may produce the output by comparing the voltages at differential amplifier output nodes 264, 262. The temperature sensor may generate a temp code based on a count of ones in COMPOUT over some period of time. Note that COMPOUT may be based on OUT and OUTN in
In step 804, the temp code output of the temperature sensor is compared to a target code. In one embodiment, the target code is a half code midway between the lowest and highest temperature code. For example, for an eight bit temperature code the half code may be 1000_0000. Note that in one embodiment, capacitors C1 and C2 are used, but capacitors C3 and C4 are not used.
In step 806 a determination is made whether the trimming process (of VBG) is done. In one embodiment, this step concludes that the process is done when the temperature code hits the target code.
If the process is not done, then VBG is adjusted in step 808. There are numerous ways in which VBG may be adjusted. In one embodiment, the resistance of resistor 222 (see
The process 800 then returns to step 804 to perform another comparison of the temperature code with the target code. Eventually when it is determined in step 806 that the trimming is complete, a trim code for trimming VBG is stored (in step 810).
In one embodiment, trimming VBG includes at least one sample phase, at least one integrate phase, and a compare phase. In one embodiment, the comparator 248 (see
Since the first sample phase involves VTRIM−VBG, the switch operation may be the same as depicted in
In step 902, a trim voltage (VTRIM) and the bandgap voltage are provided to the SDM ADC 206 (this might the SDM ADC 206 of
The comparator 248 may then produces an output (e.g., COMPOUT) based on the input to the SDM ADC 206. The temperature sensor may generate a temp code based on a count of ones in COMPOUT over some period of time.
In step 904, the temp code output of the temperature sensor is compared to a target code. In one embodiment, the target code is a half code midway between the lowest and highest temperature code. For example, for an eight bit temperature code the half code may be 1000_0000.
In step 906 a determination is made whether the trimming process (for the capacitors) is done. In one embodiment, this step concludes that the process is done when the temperature code hits the target code.
If the process 900 is not done, then the capacitors C3, C4 are adjusted in step 908. In step 908, a working trim code is stored. This is based on the adjustment made in this step.
The process 900 then returns to step 904 to perform another comparison of the temperature code with the target code. Eventually when it is determined in step 906 that the trimming is complete, a trim code is stored for the capacitors C3, C4 (in step 910).
In one embodiment, trimming of the capacitors C3 and C4 includes at least one sample phase, at least one integrate phase, and a compare phase. In one embodiment, the comparator 248 compares the voltages at nodes 262 and 264 during the compare phase. After the comparison, the comparator 248 may hold the result until the next compare phase.
Switches 3 and 4 are open. Hence, capacitor C1 is not connected to capacitor C5. Likewise, capacitor C2 is not connected to capacitor C6. Moreover, capacitor C3 is not connected to capacitor C5. Likewise, capacitor C4 is not connected to capacitor C6. Thus, during the sample phase switches 1, 2, 7, 8, 13, 16, 17, and 18 are closed. All other switches (in switches 270 and SDM ADC 206) may be open. Note that the sample phase may be used during step 902 of
Thus, during this integrate phase, switches 3, 4, 5, 6, 9, 10, 11 and 12 are closed. All other switches (in switches 270 and SDM ADC 206) may be open.
In step 1002, the present value of VPTAT and the bandgap voltage are provided to the SDM ADC 206. In one embodiment, the present value of VPTAT is provided to the non-inverting input of differential amplifier 240 and the bandgap voltage is provided to the inverting input of differential amplifier 240. This step is different from step 802 of
In step 1004, the temp code output of the temperature sensor is compared to a target code. In one embodiment, the target code is a half code midway between the lowest and highest temperature code. For example, for an eight bit temperature code the half code may be 1000_0000.
In step 1006 a determination is made whether the trimming process (for VPTAT) is done. In one embodiment, this step concludes that the process is done when the temperature code hits the target code.
If the process 1000 is not done, then VPTAT is adjusted in step 1008. In one embodiment, the resistance of resistor 220 in
The process 1000 then returns to step 1004 to perform another comparison of the temperature code with the target code. Eventually when it is determined in step 1006 that the trimming is complete, a trim code is stored for VPTAT (in step 1010.)
In one embodiment, trimming of VPTAT includes at least one sample phase, at least one integrate phase, and a compare phase. In one embodiment, the comparator 248 compares the voltages at nodes 262 and 264 during the compare phase. After the comparison, the comparator 248 may hold the result until the next compare phase.
Switches 3 and 4 are open. Hence, capacitor C1 is not connected to capacitor C5. Likewise, capacitor C2 is not connected to capacitor C6. Moreover, capacitor C3 is not connected to capacitor C5. Likewise, capacitor C4 is not connected to capacitor C6. Thus, during the sample phase switches 1, 2, 7, 8, 14, 16, 17, and 18 are closed. All other switches (in switches 270 and SDM ADC 206) may be open. Note that the sample phase may be used during step 1002 of
Thus, during the integrate phase switches 3, 4, 5, 6, 9, 10, 11 and 12 are closed. All other switches (in switches 270 and SDM ADC 206) may be open.
Some applications require a fast measurement of a physical parameter (e.g., temperature, voltage, pressure), but can tolerate a lower resolution measurement. Other applications require a higher resolution measurement, but can tolerate a slower measurement.
In one embodiment, the SDM ADC 1106 is a first order SDM. In one embodiment, the SDM ADC 1106 is a single bit SDM ADC. In one embodiment, the SDM ADC 1106 is both a first order single bit SDM ADC.
The sensor also has control logic 1108 and storage 1110(1) . . . 1110(m). The storage 1110 may be implemented with latches, RAM, or other storage. In one embodiment, “m” is at least two, wherein there are two or more storage units. Each storage unit may be configured to store a digital code having a different resolution. For example, storage 1110(1) may be configured to store a five bit digital code, storage unit 1110(2) (not depicted) may be configured to store an eight bit digital code, etc. In this example, storage 1110(1) may sample five data lines of bus 1112, storage 1110(2) may sample eight data lines of bus 1112, etc.
The digital code on the bus 1112 might not be very accurate when it is first output. For example, on the very first clock cycle after the SDM ADC 1106 first starts to generate the digital code, the digital code might not be very accurate. However, over time (with increasing clock cycles), the digital code may become more accurate.
In one embodiment, when the SDM ADC 1106 first starts to output the digital code only the least significant bit(s) have meaning. As the SDM ADC 1106 continues to update the digital code, the more significant bits have meaning. In one embodiment, after 2^n clock cycles the “n” least significant bits have meaning. For example, after 32 clock cycles (2^5), the five least significant bits have meaning, after 256 clock cycles (2^8), the eight least significant bits have meaning, after 1024 clock cycles (2^10), the ten least significant bits have meaning. A reason for this is that the SDM ADC 1106 (in combination with control logic 1108) may count ones in a stream of values output by the comparator 248 in the SDM ADC 1106. The value for the digital code may be the average number of ones over some interval.
For example, after 32 clock cycles, the digital code may be based on whether the output of the comparator 248 was a “1” or a “0” for each of the 32 clock cycles. Here, the output of the comparator 248 may refer to the “OUT” in
If there were exactly 128 “ones” in 256 clock cycles, this may correspond to a digital code of “1000_0000”. If there were exactly 64 “ls” in 256 clock cycles, this may correspond to a digital code of “0100_0000”. If there were exactly 32 “ones” in 256 clock cycles, this may correspond to a digital code of “0010_0000”. If there were exactly 16 “ones” in 256 clock cycles, this may correspond to a digital code of “0001_0000”. If there were exactly 8 “ones” in 256 clock cycles, this may correspond to a digital code of “0000_1000”. If there were exactly 4 “ones” in 256 clock cycles, this may correspond to a digital code of “0000_0100”. If there were exactly 2 “ones” in 256 clock cycles, this may correspond to a digital code of “0000_0010”. If there was exactly 1 “ones” in 256 clock cycles, this may correspond to a digital code of “0000_0001”. In each case, the eight least significant bits have a meaning, in this example.
The logic 1108 may instruct the storage 1110(1) . . . 1110(n) when to sample the bus 1112. This may be based on the number of clock cycles that have passed. For example, this may be based on the number of clock cycles that have passed since the SDM ADC first generated a digital code in response to the signal for the physical parameter. In one embodiment, latching occurs after 2^n clock cycles, where “n” is the number of bits for the code stored by the storage. For example, if storage 1110(1) stores a 5 bit digital code, the logic 1108 can instruct storage 1110(1) to store data from bus 1112 after 32 clock cycles. This may allow the respective storage units to store values based on the output of comparator 248 over 2^n consecutive clock cycles.
In step 1204, the SDM ADC 1106 puts an initial value for a digital code on the bus 1112. In one embodiment, this initial value is based on a single value of the output of comparator 248. Thus, this value could only be “1” or “0”, in one embodiment. In one embodiment, only one bit of the initial value for the digital code has a meaning. For example, only the least significant bit has a meaning for the very first digital code, in one embodiment.
In step 1206, the SDM ADC 1106 updates the digital code on the bus 1112 each clock cycle. As the digital code is updated, more bits have a meaning, in one embodiment. As discussed above, the digital code can be based on further output of the comparator 248.
In step 1208, the control logic 1108 instructs the storage to latch data from the bus 1112 after 2^r clock cycles, where “r” is the number of bits for the code stored by the storage. In one embodiment, by “2^r clock cycles after the SDM ADC first puts the digital code onto the plurality of data lines” the clock cycle in which the digital code is first output is included in the count. For example, if r=5, this refers to the 32nd clock cycle. Note that for different storage, the value of “r” may be different. For example, if r=8, this refers to storage after the 256th clock cycle. Note that over time, the values on the bus 1112 may become more accurate. Stated another way, over time more bits in the digital code have a meaning, in one embodiment.
Note that another way of stating the operation in step 1208 is in terms of clock cycles after the digital code is first output to the bus (which does not count the initial clock cycle). In this case, the control logic 1108 may instruct a first storage unit to sample “n” bits of the digital code that are on the data bus “2^n−1” clock cycles after the initial clock cycle.
The control logic 1108 may instruct a first storage unit to sample “m” bits of the digital code that are on the data bus “2^m−1” clock cycles after the initial clock cycle, wherein “m” is greater than “n”.
The PTAT generator 1302 provides a VPTAT (VPTAT) and a VBG (VBG) to the SDM-ADC 1304 in this embodiment. In one embodiment, PTAT generator 1302 is implemented with the bandgap circuit 204a of
Latch 1308 stores “L” bits, latch 1310 stores “H” bits, and latch 1312 stores “T” bits. In one embodiment, L<H<T. The counter and logic 1306 instructs latch 1308 to storage the data that is on the bus 1314 after 2^L clock cycles, instructs latch 1310 to storage the data that is on the bus 1314 after 2^H clock cycles, and instructs latch 1312 to storage the data that is on the bus 1314 after 2^T clock cycles, in one embodiment. In one embodiment, by “after some number of clock cycles” it is meant with respect to after SDM ADC placed an initial value for the code on the bus 1314. For example, latch 1308 may sample at the 32nd clock cycle, latch 1310 may sample at the 256th clock cycle, and latch 1312 may sample at the 1028th clock cycle. Latch 1308 may be read to provide an “L” bit temperature code TOUT1<L bits>, latch 1310 may be read to provide an “H” bit temperature code TOUT2<H bits>, latch 1312 may be read to provide a “T” bit temperature code TOUT3<T bits>.
In one embodiment, latch 1308 is used to provide the temperature code the fastest of the three latches. However, the resolution is the lowest of the three latches. In one embodiment, latch 1310 is used to provide a temperature code with a higher resolution than latch 1308, but at the expense of taking longer than latch 1308. In one embodiment, latch 1312 is used during trimming of the sensor. This may include trimming the PTAT generator 1302 and/or the SDM ADC 1304. Note that the logic inputs a TRIM ENABLE signal to enable a trim operation.
The circuits of
In step 1404, VPTAT and VBG are provided from a reference generator 204 to SDM ADC 206. Note that when switches 14 and 1 are closed (e.g.,
In step 1406, SDM ADC 206 is operated based on the output of the comparator 248. In one embodiment, switches 270 and switches in SDM ADC 206 are operated based on an output of comparator 248. In one embodiment, this operation is similar to operation described with respect to trimming VPTAT that was described in connection with
In step 1408, a digital TEMP code is calculated based on an output of the comparator 248. In one embodiment, this is based on a count of the number of ones output by comparator 248 in a COMPOUT signal. The digital code may be based on the average number of ones over some number of clock cycles. This step 1408 may be performed by control logic 208.
Embodiments may be practiced in various devices including, but not limited to, memory devices, systems on a chip (SoCs), computing devices, desktop computers laptop computers, notepad computers, cellular telephones, personal digital assistants, personal navigation devices, microwave ovens, refrigerators, control circuits, and other devices for which a measurement of some physical parameter (including, but not limited to, temperature) is desired. For the sake of illustration, the following is one example implementation of a memory device in which embodiments may be practiced.
One example implementation of a memory device includes a plurality of NAND strings (or other arrangements) that form a monolithic three dimensional memory structure, bit lines, word lines, and one or more control circuits. Multiple NAND strings of the plurality of NAND strings have different select gates connected to different select lines. The multiple NAND strings are connected to a common bit line. The multiple NAND strings are connected to a common word line via their respective different select gates. The one or more control circuits concurrently program multiple memory cells on the multiple NAND strings that are connected to the common bit line and the common word line.
In one example implementation, the length of the plane in the x-direction, represents a direction in which signal paths for word lines extend (a word line or SGD line direction), and the width of the plane in the y-direction, represents a direction in which signal paths for bit lines extend (a bit line direction). The z-direction represents a height of the memory device.
In one embodiment, sensor 142 includes a voltage sensor. The voltage sensor might be used to sense a voltage that is supplied (e.g., supply voltage) to various electrical circuits. The memory device 100 may adjust operating parameters based on the level of the supply voltage. The sensor 142 may be able to sense other physical parameters (e.g., current). Note that to sense different physical parameters the sensor 142 may be considered to be multiple separate sensors.
In one embodiment, a portion of the logic of the sensor 142 is implemented by control circuitry 110. For example, state machine 112 can be used in sensor control logic (see control logic 208 in
Memory device 100 includes one or more memory die 108. Each memory die 108 includes a three dimensional memory structure 126 of memory cells (such as, for example, a 3D array of memory cells), control circuitry 110, and read/write circuits 128. In other embodiments, a two dimensional array of memory cells can be used. Memory structure 126 is addressable by word lines via a row decoder 124 and by bit lines via a column decoder 132. The read/write circuits 128 include multiple sense blocks 150 including SB1, SB2, . . . , SBp (sensing circuitry) and allow a page of memory cells to be read or programmed in parallel. In some systems, a Controller 122 is included in the same memory device 100 (e.g., a removable storage card) as the one or more memory die 108. However, in other systems, the controller can be separated from the memory die 108. In some embodiments the controller will be on a different die than the memory die. In some embodiments, one Controller 122 will communicate with multiple memory die 108. In other embodiments, each memory die 108 has its own controller. Commands and data are transferred between the host 140 and Controller 122 via a data bus 120, and between Controller 122 and the one or more memory die 108 via lines 118. In one embodiment, memory die 108 includes a set of input and/or output (I/O) pins that connect to lines 118.
Memory structure 126 may comprise one or more arrays of memory cells including a 3D array. The memory structure may comprise a monolithic three dimensional memory structure in which multiple memory levels are formed above (and not in) a single substrate, such as a wafer, with no intervening substrates. The memory structure may comprise any type of non-volatile memory that is monolithically formed in one or more physical levels of arrays of memory cells having an active area disposed above a silicon substrate. The memory structure may be in a non-volatile memory device having circuitry associated with the operation of the memory cells, whether the associated circuitry is above or within the substrate.
Control circuitry 110 cooperates with the read/write circuits 128 to perform memory operations (e.g., erase, program, read, and others) on memory structure 126, and includes a state machine 112, an on-chip address decoder 114, and a power control module 116. The state machine 112 provides chip-level control of memory operations. Code and parameter storage 113 may be provided for storing operational parameters and software. In one embodiment, state machine 112 is programmable by the software stored in code and parameter storage 113. In other embodiments, state machine 112 does not use software and is completely implemented in hardware (e.g., electrical circuits).
The on-chip address decoder 114 provides an address interface between addresses used by host 140 or memory Controller 122 to the hardware address used by the decoders 124 and 132. Power control module 116 controls the power and voltages supplied to the word lines and bit lines during memory operations. It can include drivers for word line layers (discussed below) in a 3D configuration, select transistors (e.g., SGS and SGD transistors, described below) and source lines. Power control module 116 may include charge pumps for creating voltages. The sense blocks include bit line drivers. An SGS transistor is a select gate transistor at a source end of a NAND string, and an SGD transistor is a select gate transistor at a drain end of a NAND string.
Any one or any combination of sensor 142, control circuitry 110, state machine 112, decoders 114/124/132, code and parameter storage 113, power control module 116, sense blocks 150, read/write circuits 128, and Controller 122 can be considered one or more control circuits (or a managing circuit) that performs the functions described herein.
The (on-chip or off-chip) Controller 122 may comprise a processor 122c, ROM 122a, RAM 122b and a Memory Interface 122d, all of which are interconnected. Processor 122C is one example of a control circuit. Other embodiments can use state machines or other custom circuits designed to perform one or more functions. The storage devices (ROM 122a, RAM 122b) comprises code such as a set of instructions, and the processor 122c is operable to execute the set of instructions to provide the functionality described herein. Alternatively or additionally, processor 122c can access code from a storage device in the memory structure, such as a reserved area of memory cells connected to one or more word lines. Memory interface 122d, in communication with ROM 122a, RAM 122b and processor 122c, is an electrical circuit that provides an electrical interface between Controller 122 and memory die 108. For example, memory interface 122d can change the format or timing of signals, provide a buffer, isolate from surges, latch I/O, etc. Processor 122C can issue commands to control circuitry 110 (or any other component of memory die 108) via Memory Interface 122d.
Multiple memory elements in memory structure 126 may be configured so that they are connected in series or so that each element is individually accessible. By way of non-limiting example, flash memory devices in a NAND configuration (NAND flash memory) typically contain memory elements connected in series. A NAND string is an example of a set of series-connected memory cells and select gate transistors.
A NAND flash memory array may be configured so that the array is composed of multiple NAND strings of which a NAND string is composed of multiple memory cells sharing a single bit line and accessed as a group. Alternatively, memory elements may be configured so that each element is individually accessible, e.g., a NOR memory array. NAND and NOR memory configurations are exemplary, and memory cells may be otherwise configured.
The memory cells may be arranged in the single memory device level in an ordered array, such as in a plurality of rows and/or columns. However, the memory elements may be arrayed in non-regular or non-orthogonal configurations, or in structures not considered arrays.
A three dimensional memory array is arranged so that memory cells occupy multiple planes or multiple memory device levels, thereby forming a structure in three dimensions (i.e., in the x, y and z directions, where the z direction is substantially perpendicular and the x and y directions are substantially parallel to the major surface of the substrate).
As a non-limiting example, a three dimensional memory structure may be vertically arranged as a stack of multiple two dimensional memory device levels. As another non-limiting example, a three dimensional memory array may be arranged as multiple vertical columns (e.g., columns extending substantially perpendicular to the major surface of the substrate, i.e., in they direction) with each column having multiple memory cells. The vertical columns may be arranged in a two dimensional configuration, e.g., in an x-y plane, resulting in a three dimensional arrangement of memory cells, with memory cells on multiple vertically stacked memory planes. Other configurations of memory elements in three dimensions can also constitute a three dimensional memory array.
By way of non-limiting example, in a three dimensional NAND memory array, the memory elements may be coupled together to form a vertical NAND string that traverses across multiple horizontal memory device levels. Other three dimensional configurations can be envisioned wherein some NAND strings contain memory elements in a single memory level while other strings contain memory elements which span through multiple memory levels. Three dimensional memory arrays may also be designed in a NOR configuration and in a ReRAM configuration.
A person of ordinary skill in the art will recognize that the technology described herein is not limited to a single specific memory structure, but covers many relevant memory structures within the spirit and scope of the technology as described herein and as understood by one of ordinary skill in the art.
Although the example memory system discussed above is a three dimensional memory structure that includes vertical NAND strings with charge-trapping material, other (2D and 3D) memory structures can also be used with the technology described herein. For example, floating gate memories (e.g., NAND-type and NOR-type flash memory ReRAM memories, magnetoresistive memory (e.g., MRAM), and phase change memory (e.g., PCRAM) can also be used.
One example of a ReRAM memory includes reversible resistance-switching elements arranged in cross point arrays accessed by X lines and Y lines (e.g., word lines and bit lines). In another embodiment, the memory cells may include conductive bridge memory elements. A conductive bridge memory element may also be referred to as a programmable metallization cell. A conductive bridge memory element may be used as a state change element based on the physical relocation of ions within a solid electrolyte. In some cases, a conductive bridge memory element may include two solid metal electrodes, one relatively inert (e.g., tungsten) and the other electrochemically active (e.g., silver or copper), with a thin film of the solid electrolyte between the two electrodes. As temperature increases, the mobility of the ions also increases causing the programming threshold for the conductive bridge memory cell to decrease. Thus, the conductive bridge memory element may have a wide range of programming thresholds over temperature.
Magnetoresistive memory (MRAM) stores data by magnetic storage elements. The elements are formed from two ferromagnetic plates, each of which can hold a magnetization, separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity; the other plate's magnetization can be changed to match that of an external field to store memory. This configuration is known as a spin valve and is the simplest structure for an MRAM bit. A memory device is built from a grid of such memory cells. In one embodiment for programming, each memory cell lies between a pair of write lines arranged at right angles to each other, parallel to the cell, one above and one below the cell. When current is passed through them, an induced magnetic field is created.
Phase change memory (PCRAM) exploits the unique behavior of chalcogenide glass. One embodiment uses a GeTe—Sb2Te3 super lattice to achieve non-thermal phase changes by simply changing the co-ordination state of the Germanium atoms with a laser pulse (or light pulse from another source). Therefore, the doses of programming are laser pulses. The memory cells can be inhibited by blocking the memory cells from receiving the light. Note that the use of “pulse” in this document does not require a square pulse, but includes a (continuous or non-continuous) vibration or burst of sound, current, voltage light, or other wave.
One embodiment disclosed herein includes an apparatus comprising a sigma delta modulator (SDM) analog-to-digital convertor (ADC) having an input and an output that responds to the input. The apparatus further comprises logic configured to provide a proportional to absolute temperature voltage (VPTAT) minus a temperature independent reference voltage (VREF) to the input of the SDM ADC. The logic is configured to generate a digital temperature code based on the output of the SDM ADC.
One embodiment disclosed herein includes a method comprising: generating a band gap voltage (VBG); generating a proportional to absolute temperature voltage (VPTAT); providing a voltage input signal as an input to a sigma delta modulator (SDM) analog-to-digital convertor (ADC), the voltage input signal comprising the proportional to absolute temperature voltage minus the band gap voltage; and generating a digital temperature code based on an output of the SDM ADC.
One embodiment disclosed herein includes an apparatus comprising: a reference generator configured to generate a bandgap voltage and a proportional to absolute temperature voltage; a first order, single-bit sigma delta modulator (SDM) analog-to-digital convertor (ADC); and control logic configured to provide the proportional to absolute temperature voltage minus the bandgap voltage as an input of the SDM ADC. The control logic is configured to generate a digital temperature code based on an output of the SDM ADC.
One embodiment disclosed herein includes apparatus comprising reference voltage generation means for generating a band gap voltage (VBG). The reference voltage generation means further for generating a proportional to absolute temperature voltage (VPTAT). The apparatus further comprises control means for providing the proportional to absolute temperature voltage minus the band gap voltage as an input of a sigma delta modulator (SDM) analog-to-digital convertor (ADC), wherein the control means is further for generating a digital temperature code based on an output of the SDM ADC.
A reference voltage generation means for generating a band gap voltage (VBG), in various embodiments, may include reference generator 204, band gap circuit 204a, bandgap circuit 204b, diodes (e.g., diodes D1, D2 and D3), resistors (e.g., resistors 220, 222, 224), transistors (e.g., transistors 210, 212, 213, 214, 228, 230, 217-276), switches (e.g., DEM switches 218, switches 226, 277, 278), operational amplifiers (e.g., operational amplifier 279) and/or other hardware. Other embodiments may include similar or equivalent means for generating a band gap voltage.
A control means for providing the proportional to absolute temperature voltage minus the band gap voltage as an input of a sigma delta modulator (SDM) analog-to-digital convertor (ADC), in various embodiments, may include control logic 208, switches 251-260, switches 1-18, capacitors C1-C4, switches 270, control circuitry 110, state machine 112, controller 122, processor 122c, transistors, and/or other hardware. Other embodiments may include similar or equivalent means for providing the proportional to absolute temperature voltage minus the band gap voltage as an input of a sigma delta modulator (SDM) analog-to-digital convertor (ADC).
A control means that is further for generating a digital temperature code based on an output of the SDM ADC, in various embodiments, may include control logic 208, switches 270, switches 251-260, switches 1-18, capacitors C1-C6, switches 270, compare logic 248, control circuitry 110, state machine 112, controller 122, processor 122c, transistors, and/or other hardware. Other embodiments may include similar or equivalent means for generating a digital temperature code based on an output of the SDM ADC.
One embodiment disclosed herein includes an apparatus, comprising: a sigma delta modulator (SDM) analog-to-digital convertor (ADC) configured to receive an analog signal and to output each bit of a digital code for the analog signal to a different data line of a plurality of data lines. The SDM ADC is configured to update the digital code on the plurality of data lines in accordance with a clock signal. The apparatus further comprises a plurality of storage units. Each storage unit is coupled to data lines of the plurality of data lines that provide “r” least significant bits of the digital code, wherein “r” is a different number for at least two of the plurality of storage units. The apparatus further comprises control logic configured to instruct respective storage units of the plurality of storage units to sample the “r” data lines to which the respective storage unit is coupled 2^r clock cycles after the SDM ADC first puts the digital code onto the plurality of data lines.
One embodiment disclosed herein includes a method comprising: inputting an analog signal into a sigma delta modulator (SDM) analog-to-digital convertor (ADC); outputting an initial value for a digital code for the analog signal, by the SDM ADC, onto a data bus during a first clock cycle; outputting an updated digital code for the analog signal, by the SDM ADC, onto the data bus for each clock cycle after the first clock cycle; instructing a first storage unit to sample “n” bits of the digital code that are on the data bus “2^n−1” clock cycles after the first clock cycle; and instructing a second storage unit to sample “m” bits of the digital code that are on the data bus “2^m−1” clock cycles after the first clock cycle, wherein “m” is greater than “n”.
One embodiment disclosed herein includes an apparatus comprising: a reference voltage generator configured to generate a bandgap voltage and a proportional to temperature voltage; a single-bit, first-order sigma delta modulator (SDM) analog-to-digital convertor (ADC) coupled to the reference voltage generator; and a bus having data lines coupled to the SDM ADC. The SDM ADC is configured to output a digital code having a least significant bit and a most significant bit onto the data lines. The SDM ADC is configured to update the digital code each cycle of a clock signal. The apparatus further comprises a first storage unit coupled to “n” of the data lines that provide the “n” least significant bits of the digital code; a second storage unit coupled to “m” of the data lines that provide the “m” least significant bits of the digital code, wherein “m” is greater than “n”; and control logic configured to instruct the first storage unit to sample the “n” data lines that provide the “n” least significant bits of the digital code 2^n clock cycles after the SDM ADC first puts the digital code onto the bus and to instruct the second storage unit to sample the “m” data lines that provide the “m” least significant bits of the digital code 2^m clock cycles after the SDM ADC first puts the digital code onto the bus.
One embodiment disclosed herein includes an apparatus comprising: reference voltage generator means for generating a bandgap voltage and a proportional to temperature voltage; analog-to-digital conversion means for converting an analog signal to a digital code and outputting the digital code, wherein the analog-to-digital conversion means is for performing sigma delta modulation on the analog signal, wherein the analog-to-digital conversion means is for updating the digital code in accordance with a clock signal; a plurality of storage means for storing the “r” least significant bits of the digital code, wherein at least two of the plurality of storage means have a different value for “r”; and control means for instructing the respective storage means to sample the digital code 2^r clock cycles after an initial digital code is output by the analog-to-digital conversion means.
A reference voltage generator means for generating a bandgap voltage and a proportional to temperature voltage, in various embodiments, may include reference generator 204, band gap circuit 204a, bandgap circuit 204b, diodes (e.g., diodes D1, D2 and D3), resistors (e.g., resistors 220, 222, 224), transistors (e.g., transistors 210, 212, 213, 214, 228, 230, 217-276), switches (e.g., DEM switches 218, switches 226, 277, 278), operational amplifiers (e.g., operational amplifier 279) and/or other hardware. Other embodiments may include similar or equivalent means for generating a bandgap voltage and a proportional to temperature voltage.
An analog-to-digital conversion means for converting an analog signal to a digital code and outputting the digital code, in various embodiments, may include SDM ADC 206, amplifier 240, compare logic 248, control logic 208, capacitors C1-C6, switches 251-260, switches 1-18, and/or other hardware. Other embodiments may include similar or equivalent means for converting an analog signal to a digital code and outputting the digital code.
An analog-to-digital conversion means is for performing sigma delta modulation on the analog signal, in various embodiments, may include SDM ADC 206, amplifier 240, compare logic 248, control logic 208, capacitors C1-C6, switches 251-260, switches 1-18, and/or other hardware. Other embodiments may include similar or equivalent means for performing sigma delta modulation on the analog signal.
An analog-to-digital conversion means for updating the digital code in accordance with a clock signal, in various embodiments, may include SDM ADC 206, amplifier 240, compare logic 248, control logic 208, capacitors C1-C6, switches 251-260, switches 1-18, and/or other hardware. Other embodiments may include similar or equivalent means for updating the digital code in accordance with a clock signal.
A plurality of storage means for storing the “r” least significant bits of the digital code, in various embodiments, may include, latches 1110(1)-1110(n); latches 1308, 1310, 1312; and/or other hardware. Other embodiments may include similar or equivalent means for storing the “r” least significant bits of the digital code.
Control means for instructing the respective storage means to sample the digital code 2^r clock cycles after an initial digital code is output by the analog-to-digital conversion means, in various embodiments, may include, control logic 1108, control circuitry 110, state machine 112, controller 122, processor 122c, digital logic, an ASIC (Application Specific Integrated Circuit), RAM, and/or ROM, and/or other hardware. Other embodiments may include similar or equivalent means for storing the “r” least significant bits of the digital code.
For purposes of this document, it should be noted that the dimensions of the various features depicted in the figures may not necessarily be drawn to scale.
For purposes of this document, reference in the specification to “an embodiment,” “one embodiment,” “some embodiments,” or “another embodiment” may be used to describe different embodiments or the same embodiment.
For purposes of this document, a connection may be a direct connection or an indirect connection (e.g., via one or more others parts). In some cases, when an element is referred to as being connected or coupled to another element, the element may be directly connected to the other element or indirectly connected to the other element via intervening elements. When an element is referred to as being directly connected to another element, then there are no intervening elements between the element and the other element. Two devices are “in communication” if they are directly or indirectly connected so that they can communicate electronic signals between them.
For purposes of this document, the term “based on” may be read as “based at least in part on.”
For purposes of this document, without additional context, use of numerical terms such as a “first” object, a “second” object, and a “third” object may not imply an ordering of objects, but may instead be used for identification purposes to identify different objects.
For purposes of this document, the term “set” of objects may refer to a “set” of one or more of the objects.
The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the proposed technology and its practical application, to thereby enable others skilled in the art to best utilize it in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope be defined by the claims appended hereto.
Claims
1. An apparatus, comprising:
- a sigma delta modulator (SDM) analog-to-digital convertor (ADC) having an input and an output that responds to the input; and
- logic configured to provide a proportional to absolute temperature voltage minus a temperature independent reference voltage to the input of the SDM ADC, the logic configured to generate a digital temperature code based on the output of the SDM ADC.
2. The apparatus of claim 1, wherein the temperature independent reference voltage is a bandgap voltage.
3. The apparatus of claim 1, further comprising:
- a reference generator configured to generate the proportional to absolute temperature voltage and the temperature independent reference voltage.
4. The apparatus of claim 3, wherein the reference generator is configured to compensate for offsets due to mismatched components within the reference generator.
5. The apparatus of claim 1, wherein the SDM ADC is a one bit SDM ADC.
6. The apparatus of claim 1, wherein the SDM ADC is a first order SDM ADC.
7. The apparatus of claim 1, wherein the SDM ADC comprises:
- a fully differential amplifier having inputs; and
- a switched capacitor network having a plurality of capacitors coupled to the inputs of the fully differential amplifier, the plurality of capacitors configured to scale the temperature independent reference voltage.
8. The apparatus of claim 7, wherein the switched capacitor network is configured to scale the temperature independent reference voltage such that the digital temperature code has a step size of a fixed amount of degrees Celsius per code in the digital temperature code.
9. The apparatus of claim 8, wherein the logic is configured to trim one or more capacitors in the switched capacitor network to establish a scaling factor (K), wherein at a target temperature: the scaling factor multiplied by the temperature independent reference voltage depends on the proportional to absolute temperature voltage minus the temperature independent reference voltage.
10. The apparatus of claim 9, wherein a ratio of capacitance of a first capacitor to a second capacitor in the switched capacitor network equals the scaling factor.
11. A method comprising:
- generating a band gap voltage;
- generating a proportional to absolute temperature voltage;
- providing a voltage input signal as an input to a sigma delta modulator (SDM) analog-to-digital convertor (ADC), the voltage input signal comprising the proportional to absolute temperature voltage minus the band gap voltage; and
- generating a digital temperature code based on an output of the SDM ADC.
12. The method of claim 11, further comprising:
- scaling the band gap voltage such that the digital temperature code has a step size of a fixed amount of degrees Celsius per code in the digital temperature code.
13. The method of claim 12, further comprising:
- trimming a capacitance ratio of capacitors in a switched capacitor network in the SDM ADC to establish the scaling of the band gap voltage.
14. The method of claim 13, further comprising:
- trimming the band gap voltage prior to trimming the capacitance ratio of the capacitors; and
- trimming the proportional to absolute temperature voltage after trimming the capacitance ratio of the capacitors.
15. An apparatus comprising:
- a reference generator configured to generate a bandgap voltage and a proportional to absolute temperature voltage;
- a first order, single-bit sigma delta modulator (SDM) analog-to-digital convertor (ADC); and
- control logic configured to provide the proportional to absolute temperature voltage minus the bandgap voltage as an input of the SDM ADC, the control logic configured to generate a digital temperature code based on an output of the SDM ADC.
16. The apparatus of claim 15, wherein:
- the SDM ADC comprises a plurality of capacitors;
- during a sample phase the control logic is configured to provide the proportional to absolute temperature voltage to a first capacitor of the capacitors, to provide the bandgap voltage to a second capacitor of the capacitors, to provide ground to a third capacitor of the capacitors, and to provide the bandgap voltage to a fourth capacitor of the capacitors;
- during an integration phase the control logic is configured to connect the first capacitor and the third capacitor to a first input of the SDM ADC and to connect the second capacitor and the fourth capacitor to a second input of the SDM ADC; and
- a ratio of the fourth capacitor to the second capacitor scales the bandgap voltage such that the digital temperature code has a step size of one degree Celsius per code in the digital temperature code.
17. The apparatus of claim 15, wherein the SDM ADC comprises:
- a fully differential amplifier having a non-inverting input, an inverting input, a first output and a second output;
- a first integrating capacitor connected between the first output and the non-inverting input;
- a second integrating capacitor connected between the second output and the inverting input;
- a first input capacitor, a second input capacitor, a third input capacitor, and a fourth input capacitor configured in a switched capacitor network,
- wherein the control logic is configured to cause the first input capacitor to sample the proportional to absolute temperature voltage and to cause the second input capacitor to sample the bandgap voltage;
- wherein the control logic is configured to connect the first input capacitor to the non-inverting input after the first capacitor samples the proportional to absolute temperature voltage;
- wherein the control logic is configured to connect the second input capacitor to the inverting input after the second input capacitor samples the bandgap voltage.
18. The apparatus of claim 17, wherein the control logic is configured to cause the first input capacitor to sample the proportional to absolute temperature voltage, the second input capacitor to sample the bandgap voltage, the third input capacitor to sample ground, and the fourth input capacitor to sample the bandgap voltage; and
- wherein the control logic is configured to connect the first input capacitor to the non-inverting input after the first input capacitor samples the proportional to absolute temperature voltage, connect the second input capacitor to the inverting input after the second input capacitor samples the bandgap voltage, connect the third input capacitor to the non-inverting input after the third input capacitor samples ground, and connect the fourth input capacitor to the inverting input after the fourth input capacitor samples the bandgap voltage.
19. An apparatus, comprising:
- reference voltage generation means for generating a band gap voltage, the reference voltage generation means further for generating a proportional to absolute temperature voltage; and
- control means for providing the proportional to absolute temperature voltage minus the band gap voltage as an input of a sigma delta modulator (SDM) analog-to-digital convertor (ADC), wherein the control means is further for generating a digital temperature code based on an output of the SDM ADC.
20. The apparatus of claim 19, further comprising:
- scaling means for scaling the band gap voltage such that the digital temperature code has a step size of a fixed amount of degrees Celsius per code in the digital temperature code.
| 5559514 | September 24, 1996 | Thomson |
| 6008685 | December 28, 1999 | Kunst |
| 8096707 | January 17, 2012 | Raychowdhury et al. |
| 9705525 | July 11, 2017 | Singh |
| 20040004994 | January 8, 2004 | Wu et al. |
| 20130120930 | May 16, 2013 | Temkine |
| 20130218512 | August 22, 2013 | Kim |
| 20140269839 | September 18, 2014 | Tai |
| 20150369674 | December 24, 2015 | Ma |
| 20160054747 | February 25, 2016 | Cohen |
| 2295944 | January 2010 | EP |
Type: Grant
Filed: Jun 9, 2016
Date of Patent: Jul 17, 2018
Patent Publication Number: 20170257113
Assignee: SanDisk Technologies LLC (Addison, TX)
Inventor: Saurabh Kumar Singh (Bangalore)
Primary Examiner: Andre Allen
Application Number: 15/178,363
International Classification: G01K 7/34 (20060101); G05F 3/24 (20060101); H03M 3/00 (20060101);
